For the purposes of checking the quality and in particular the degree of uniformity of a pneumatic tire such as a motor vehicle tire, a tire may be mounted on a rotary device having measuring rims. The tire can then be pressed under a given loading against a test surface which may be in the form of a rotating testing drum or an endless circulating belt. While the tire is rolled against the test surface, radial, lateral and tangential force fluctuations are measured, to provide information about the uniformity and thus the quality of the tire being tested. For example `Automobile-Industrie` 2/71, pages 85 through 90, in an article by Peter M. Gruber `Reifenungleichformigkeit--Ursache und Wirkung` [`Tire non-uniformity--cause and Effect`] describes processes and apparatuses for testing the uniformity of pneumatic tires.
However, the forel fluctuations that are detected in the above-discussed processes and apparatuses do not just result from irregularities or non-uniformities of the tire itself, but may include force fluctuation components which are to be attributed to alterations and variations in arrangement of the measuring system itself. For example, in spite of sensitive regulation of the inflation pressure of the tire being tested, it is not possible to maintain an absolutely constant inflation pressure in the tire throughout a measuring run. Although the inflation pressure of the tire being tested may be controlled or regulated, in which, for example, a reference may be made to EP 0 265 037 Al, it is not possible to provide an absolutely constant inflation pressure throughout the testing operation, if the equipment used for and expenditure incurred in regulating the tire inflation pressure is to be kept at a commercially viable level.